Energy beam position verification

ABSTRACT

A method for verifying a position of an energy beam spot, said method comprising the steps of: providing a calibrated energy beam having a first focus in a at least two positions at a work table, detecting said at least two positions of said energy beam spot on said work table created with said energy beam having said first focus, providing said calibrated energy beam having a second focus in said at least two positions at a work table, detecting said at least two positions of said energy beam spot on said work table created with said energy beam having said second focus, comparing said at least two positions created with said first and second focus, wherein said position of the energy beam is verified if said positions created with said first focus are deviating less than a predetermined distance from said positions created with said second focus.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalPatent Application Ser. No. 62/039,626, filed Aug. 20, 2014; U.S.Provisional Patent Application Ser. No. 62/093,882, filed Dec. 18, 2014;and U.S. Provisional Patent Application Ser. No. 62/097,328, filed Dec.29, 2014; the contents of all of which as are hereby incorporated byreference in their entirety.

BACKGROUND

1. Related Field

Various embodiments of the present invention relate to a method andassociated systems for position verification of an energy beam.Consolidated position, size and deflection speed verification methodsand systems are also provided.

2. Description of Related Art

Freeform fabrication or additive manufacturing is a method for formingthree-dimensional articles through successive fusion of chosen parts ofpowder layers applied to a worktable. A method and apparatus accordingto this technique is disclosed in US 2009/0152771.

Such an apparatus may comprise a work table on which thethree-dimensional article is to be formed, a powder dispenser, arrangedto lay down a thin layer of powder on the work table for the formationof a powder bed, an energy beam source for delivering an energy beamspot to the powder whereby fusion of the powder takes place, elementsfor control of the energy beam spot over the powder bed for theformation of a cross section of the three-dimensional article throughfusion of parts of the powder bed, and a controlling computer, in whichinformation is stored concerning consecutive cross sections of thethree-dimensional article. A three-dimensional article is formed throughconsecutive fusions of consecutively formed cross sections of powderlayers, successively laid down by the powder dispenser.

In order to melt the powder material at specific locations there is aneed to inter alia verify the position of the energy beam spot. Oneneeds to know that the desired position of the energy beam correspond tothe actual position of the energy beam. There is a need in the art for asimple and efficient method for verifying the position of an energybeam.

Still further, in order to melt the powder material at specificlocations there is a need to inter alia verify the size of the beamspot. One needs to know that different power levels of the energy beamat different areas of the powder bed correspond to the desired beam spotsizes. There is a need in the art for a simple and efficient method forverifying the beam spot size of an energy beam such as a laser beam oran electron beam. Yet still further, in order to melt the powdermaterial at specific locations, there is a need to inter alia verify thedeflection speed of the energy beam spot. One needs to know thatdifferent deflection speeds at different areas of the powder bedcorrespond to the desired deflection speeds. There is a need in the artfor a simple and efficient method for verifying the deflection speed ofan energy beam such as a laser beam or an electron beam.

BRIEF SUMMARY

Having this background, an object of the invention is to provide methodsand associated systems for verifying a position of an energy beam, whichis less complex than prior art methods. The above-mentioned object isachieved by the features according to the claims contained herein.

In a first aspect of the invention it is provided a method for verifyinga position of an energy beam spot, the method comprising the steps of:providing an energy beam having a first focus in at least two positionson a work table, detecting the at least two positions of the energy beamspot on the work table created with the energy beam having the firstfocus, providing the energy beam having a second focus in the at leasttwo positions on a work table, detecting the at least two positions ofthe energy beam spot on the work table created with the energy beamhaving the second focus, comparing the at least two positions createdwith the first and second focuses, wherein the position of the energybeam is verified if the at least two positions created with the firstfocus are deviating less than a predetermined distance from the at leasttwo positions created with the second focus.

An exemplary and non-limiting advantage of this method is that thelateral position of the work table is not required to be known forverifying the deflection speed of the energy beam. Another exemplary andnon-limiting advantage is that the angle of the work table is notrequired to be known for verifying the deflection speed of the energybeam. Still another exemplary and non-limiting advantage of the presentinvention is that it provides for a simple method for verifying aposition stability of an energy beam.

In another example embodiment the at least two positions are arranged ina regularly 2-dimensional pattern. An exemplary and non-limitingadvantage of this embodiment is that any type of pattern may be used forverifying the position. The only requirement is that the same pattern isused for the different focuses.

In another example embodiment the at least two positions are provided atidentical positions as in a calibration process. An exemplary andnon-limiting advantage of this embodiment is that any errors that may becaused by using different patterns in the calibration process and theverification process may be eliminated.

In still another example embodiment of the present invention the energybeam spot is a laser beam spot or an electron beam spot. An exemplaryand non-limiting advantage of this example embodiment is that it isapplies equally to a laser based system as to an electron beam basedsystem.

In still another example embodiment of the present invention thepositions may be detected by an IR-camera, a CCD-camera, a digitalcamera, a CMOS camera or a NIR-camera. An exemplary and non-limitingadvantage of this example embodiment is that almost all types of camerasmay be used for detecting the position of the energy beam on the worktable.

In still another example embodiment the predetermined distance is lessthan 100 μm. An exemplary and non-limiting advantage of this embodimentis that relatively small deviations, in the order of the beam spot size,may relatively easily be detected depending on the resolution of thecamera used.

In still another example embodiment the method further comprising a stepof sending out a warning signal if any one of the at least two positionsprovided with the first focus is deviating more than the predetermineddistance from the at least two positions provided with the second focus.An exemplary and non-limiting advantage of this embodiment is thatdeviating positions indicating a non-calibrated deflection speed maybesent out as a warning signal/message to a user of the energy beamdeflection equipment. A large enough deviation in position may alsoswitch off the beam deflection equipment.

In still another example embodiment of the present invention the worktable is provided with a reference pattern. An exemplary andnon-limiting advantage of this embodiment is that the relative positionof the energy beam may be determined.

In still another example embodiment the at least two positions areprovided on the work table having a temperature above 500° C. Anexemplary and non-limiting advantage of this embodiment is that it workequally well on cold surface as well as hot surfaces. This is also trueof the calibration was made on a cold surface and the verification ismade on a hot surface, i.e., the calibration may be performed at roomtemperature and the verification process may be performed at atemperature above 500° C. without achieving erroneous verificationresults.

In another aspect of the present invention it is provided a use of averifying method according to any one of the disclosed embodiment in anadditive manufacturing apparatus in which the energy beam spot is usedfor fusing powder material layerwise for forming three-dimensionalarticles. An exemplary and non-limiting advantage of this embodiment isthat the accuracy of build 3-dimensional parts may further be improved.

In still another aspect of the present invention it is provided a methodfor forming a three-dimensional article through successively depositingindividual layers of powder material that are fused together with atleast one energy beam so as to form the article, the method comprisingthe steps of: generating a model of the three dimensional article,applying a first powder layer on a work table, directing the energy beamfrom at least one energy beam source over the work table, causing thefirst powder layer to fuse in selected locations according to the modelto form a first cross section of said three dimensional article, themethod further comprising a verification method for verifying a positionof the energy beam used for fusing the powder material, the verificationmethod comprising the steps of: providing the energy beam having a firstfocus in at least two positions on the work table, detecting the atleast two positions of the energy beam spot on the work table createdwith the energy beam having the first focus, providing the energy beamhaving a second focus in the at least two positions on the work table,detecting the at least two positions of the energy beam spot on the worktable created with the energy beam having the second focus, comparingthe at least two positions created with the first and second focuses,wherein the position of the energy beam is verified if the at least twopositions created with the first focus are deviating less than apredetermined distance from the at least two positions created with thesecond focus.

In an example embodiment of the method for forming the three-dimensionalarticle, the verification of the energy beam position may be performedbefore each layer of the three-dimensional article is fused.Alternatively the verification step is performed every 5^(th) layer,10^(th), 25^(th) layer or before starting to build a newthree-dimensional article.

In still another aspect of the present invention it is provided anon-transitory computer program product comprising at least onenon-transitory computer-readable storage medium having computer-readableprogram code portions embodied therein. The computer-readable programcode portions comprise: at least one executable portion configured for:providing the energy beam having a first focus in at least two positionson the work table, detecting the at least two positions of the energybeam spot on the work table created with the energy beam having thefirst focus, providing the energy beam having a second focus in the atleast two positions on the work table, and detecting the at least twopositions of the energy beam spot on the work table created with theenergy beam having the second focus, and at least one executable portionconfigured for comparing the at least two positions created with thefirst and second focuses, wherein the position of the energy beam isverified if the at least two positions created with the first focus aredeviating less than a predetermined distance from the at least twopositions created with the second focus.

In still another aspect of the present invention the non-transitorycomputer program product may be further configured for verifying atleast one of a deflection speed or a beam spot size with respect to theenergy beam. In certain embodiments for verifying a deflection speed,the computer program product may further comprise: an executable portionconfigured for generating a predetermined pattern on a work table withthe energy beam spot while deflecting the energy beam spot with a firstdeflection speed; an executable portion configured for detecting firstpositions of the energy beam spot on the work table created with thefirst deflection speed; an executable portion configured for generatingthe predetermined pattern on a work table with the energy beam spotwhile deflecting the energy beam spot with a second deflection speed; anexecutable portion configured for detecting second positions of theenergy beam spot on the work table created with the second deflectionspeed; and an executable portion configured for comparing the first andsecond positions, wherein the deflection speed is verified if each oneof the first positions are deviating less than a predetermined distancefrom corresponding ones of the second positions.

In certain embodiments for verifying a beam spot size, the computerprogram computer program product further comprises: an executableportion configured for generating a first energy beam spot from a firstenergy beam source having a predetermined size and power at a firstposition on a work piece, an executable portion configured for varyingat least one of a focus lens setting or an astigmatism lens setting forthe first energy beam spot until max intensity for the first beam spotis detected, an executable portion configured for comparing at least onesetting of the focus lens and/or astigmatism lens for the detectedmaximum intensity of the first energy beam spot with correspondingstored settings of the focus lens and/or astigmatism lens for the firstenergy beam spot with the predetermined size and power, an executableportion configured for repeating the generating, varying, and comparingsteps for different predetermined beam powers, and an executable portionconfigured for repeating the generating, varying, comparing, and therepetition thereof steps for different positions on the work piece,wherein the first energy beam spot size is verified if each detectedsettings of the focus lens and/or astigmatism lens are deviating lessthan a predetermined value from corresponding stored settings of thefocus lens and/or astigmatism lens.

In still another aspect of the present invention an apparatus forverifying a position of an energy beam spot is provided. The apparatuscomprises: at least one energy beam source configured to generate atleast one energy beam; and a control unit. The control unit isconfigured to: provide the at least one energy beam having a first focusin at least two positions on a work table, detect the at least twopositions of the energy beam spot on the work table created with the atleast one energy beam having the first focus, provide the at least oneenergy beam having a second focus in the at least two positions on awork table, detect the at least two positions of the energy beam spot onthe work table created with the at least one energy beam having thesecond focus, and compare the at least two positions created with thefirst and second focuses, wherein the position of the energy beam isverified if the at least two positions created with the first focus aredeviating less than a predetermined distance from the at least twopositions created with the second focus.

In certain embodiments, the apparatus is further configured forverifying at least one of a deflection speed or a beam spot size withrespect to the energy beam. Where verifying a deflection speed, thecontrol unit is further configured to: generate a predetermined patternon a work table with the energy beam spot while deflecting the energybeam spot with a first deflection speed; detect first deflectionpositions of the energy beam spot on the work table created with thefirst deflection speed; generate the predetermined pattern on a worktable with the energy beam spot while deflecting the energy beam spotwith a second deflection speed; detect second deflection positions ofthe energy beam spot on the work table created with the seconddeflection speed; and compare the first and second deflection positions,wherein the deflection speed is verified if each one of the firstdeflection positions are deviating less than a predetermined distancefrom corresponding ones of the second deflection positions.

Where verifying the beam spot size, the control unit is furtherconfigured to: vary at least one of a focus lens setting or anastigmatism lens setting for the first energy beam spot until maxintensity for the first beam spot is detected, compare at least onesetting of the focus lens and/or astigmatism lens for the detectedmaximum intensity of the first energy beam spot with correspondingstored settings of the focus lens and/or astigmatism lens for the firstenergy beam spot with the predetermined size and power, repeat thegenerating, varying, and comparing steps for one or more beam powersother than the predetermined beam power, and repeat the generating,varying, comparing, and the above repeating steps for one or morepositions on the work piece other than the first position, wherein thefirst energy beam spot size is verified if each detected settings of thefocus lens and/or astigmatism lens are deviating less than apredetermined value from corresponding stored settings of the focus lensand/or astigmatism lens.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 depicts a schematic side view of an electron beam and itsposition variations when the electron beam focus is varied;

FIG. 2 depicts a schematic perspective view of an example embodiment ofa setup for verifying a position of an energy beam;

FIG. 3 depicts a schematic side view of an apparatus in which theinventive verifying method may be implemented;

FIG. 4 depicts a schematic flow chart of the method according to anembodiment of the present invention;

FIG. 5 depicts a deflection correction vs. focus;

FIG. 6 depicts astigmatism correction vs. focus;

FIG. 7 depicts two energy beam pattern from two different focus on topof each other;

FIG. 8 is a block diagram of an exemplary system 1020 according tovarious embodiments;

FIG. 9A is a schematic block diagram of a server 1200 according tovarious embodiments; and

FIG. 9B is a schematic block diagram of an exemplary mobile device 1300according to various embodiments.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

Various embodiments of the present invention will now be described morefully hereinafter with reference to the accompanying drawings, in whichsome, but not all embodiments of the invention are shown. Indeed,embodiments of the invention may be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure willsatisfy applicable legal requirements. Unless otherwise defined, alltechnical and scientific terms used herein have the same meaning ascommonly known and understood by one of ordinary skill in the art towhich the invention relates. The term “or” is used herein in both thealternative and conjunctive sense, unless otherwise indicated. Likenumbers refer to like elements throughout.

Still further, to facilitate the understanding of this invention, anumber of terms are defined below. Terms defined herein have meanings ascommonly understood by a person of ordinary skill in the areas relevantto the present invention. Terms such as “a”, “an” and “the” are notintended to refer to only a singular entity, but include the generalclass of which a specific example may be used for illustration. Theterminology herein is used to describe specific embodiments of theinvention, but their usage does not delimit the invention, except asoutlined in the claims.

The term “three-dimensional structures” and the like as used hereinrefer generally to intended or actually fabricated three-dimensionalconfigurations (e.g., of structural material or materials) that areintended to be used for a particular purpose. Such structures, etc. may,for example, be designed with the aid of a three-dimensional CAD system.

The term “electron beam” as used herein in various embodiments refers toany charged particle beam. The sources of charged particle beam caninclude an electron gun, a linear accelerator and so on.

FIG. 3 depicts an example embodiment of a freeform fabrication oradditive manufacturing apparatus 300 in which the inventive verificationmethod may be implemented. The apparatus 300 in at least this embodimentcomprises an electron gun 302; a camera 304; two powder hoppers 306,307; a start plate 316; a build tank 312; a powder distributor 310; abuild platform 314; and a vacuum chamber 320.

The vacuum chamber 320 is capable of maintaining a vacuum environment bymeans of or via a vacuum system, which system may comprise aturbomolecular pump, a scroll pump, an ion pump and one or more valveswhich are well known to a skilled person in the art and therefore needno further explanation in this context. The vacuum system may becontrolled by a control unit 350.

The electron gun 302 is generating an electron beam which may be usedfor melting or fusing together powder material 318 provided on the startplate 316. The electron gun 302 may be provided in the vacuum chamber320. The control unit 350 may be used for controlling and managing theelectron beam emitted from the electron beam gun 302. At least onefocusing coil (not shown), at least one deflection coil (not shown) andan electron beam power supply (not shown) may be electrically connectedto the control unit 350. In an example embodiment of the invention theelectron gun generates a focusable electron beam with an acceleratingvoltage of about 60 kV and with a beam power in the range of 0-10 kW.The pressure in the vacuum chamber may be in the range of 1×10⁻³-1×10⁻⁶mBar when building the three-dimensional article by fusing the powderlayer by layer with the energy beam.

Instead of melting the powder material with an electron beam a laserbeam may be used. The vacuum chamber may be optional when using a laserbeam source instead of the electron beam source.

The powder hoppers 306, 307 comprise the powder material to be providedon the start plate 316 in the build tank 312. The powder material mayfor instance be pure metals or metal alloys such as titanium, titaniumalloys, aluminum, aluminum alloys, stainless steel, Co—Cr—W alloy, etc.

The powder distributor 310 is arranged to lay down a thin layer of thepowder material on the start plate 316. During a work cycle the buildplatform 314 will be lowered successively in relation to the ray gunafter each added layer of powder material. In order to make thismovement possible, the build platform 314 is in one embodiment of theinvention arranged movably in vertical direction, i.e., in the directionindicated by arrow P. This means that the build platform 314 starts inan initial position, in which a first powder material layer of necessarythickness has been laid down on the start plate 316. A first layer ofpowder material may be thicker than the other applied layers. The reasonfor starting with a first layer which is thicker than the other layersis that one does not want a melt-through of the first layer onto thestart plate. The build platform is thereafter lowered in connection withlaying down a new powder material layer for the formation of a new crosssection of a three-dimensional article. Means for lowering the buildplatform 314 may for instance be through a servo engine equipped with agear, adjusting screws etc.

A model of the three dimensional article may be generated via a CAD(Computer Aided Design) tool.

After a first layer is finished, i.e., the fusion of powder material formaking a first layer of the three-dimensional article, a second powderlayer is provided on the work table 316. The second powder layer isdistributed according to the same manner as the previous layer. However,there might be alternative methods in the same additive manufacturingmachine for distributing powder onto the work table. For instance, afirst layer may be provided by means of or via a first powderdistributor, a second layer may be provided by another powderdistributor. The design of the powder distributor is automaticallychanged according to instructions from the control unit. A powderdistributor in the form of a single rake system, i.e., where one rake iscatching powder fallen down from both a left powder hopper 306 and aright powder hopper 307, the rake as such can change design.

After having distributed the second powder layer on the work table 316,the energy beam is directed over the work table causing the secondpowder layer to fuse in selected locations to form a second crosssection of the three-dimensional article. Fused portions in the secondlayer may be bonded to fused portions of the first layer. The fusedportions in the first and second layer may be melted together by meltingnot only the powder in the uppermost layer but also remelting at least afraction of a thickness of a layer directly below the uppermost layer.

FIG. 2 depicts a schematic perspective view an example embodiment of asetup 200 for verifying a position of an energy beam. The setup 200comprises an electron beam source 210, a camera 230, a control unit 240and a work table 250.

The electron beam source is used for generating an electron beam 260which may be deflected on the work table 250 by means of or via at leastone deflection coil 130, see FIG. 1. By changing a steering current tothe at least one deflection coil 130 the electron beam 260, 140 may bemoved at any desired position within a predetermined maximum area.

An example embodiment of verifying the position of an energy beam may ina first step 410 start with providing an energy beam having a firstfocus in at least two different positions 270 on the work table 250. Theat least two positions may be arranged one-dimensionally ortwo-dimensionally. The verification process may work with a perfectlyflat work table 250 as well as with a work table 250 not being perfectlyflat, i.e., the position of the work table as well as the angle of thework table may not be known prior to the verification process. The exactposition and angle of the work table is not a prerequisite for thisverification process.

In an example embodiment the energy beam 260 may be calibrated prior tothe first step, i.e., this method may be a verification of a previouscalibration.

In another example embodiment, the energy beam may not be calibratedprior to the verification method. The verification process may be usedin a feed-back loop to at least one deflection control unit 350 foradjusting/correcting the position of the energy beam in case of anymisalignment.

The calibration procedure of the energy beam could be performed asfollows.

Step A: For a specific beam power and for a specific x and y point inthe work table the spot size is minimized by changing the current infocus 120 and astigmatic 115 coils. This could be done with for instancea camera and/or some other beam profiling equipment. The values of theastigmatism settings and focus settings are stored in the control unit140, 240.

Step B: For the same position and for the same beam power, change focusto a predetermined value. Then the astigmatic coil 115 signals areoptimized such that the beam spot size will be circular and at the sametime the deflection coil 130 signals are optimized to put the center ofthe beam spot in the same x and y point. The values of the astigmatismsettings and focus settings are stored.

Step C: Change focus to a new value and repeat step B.

Step D: Repeat step A-C for different positions.

Step E: Repeat step A-D for different beam powers.

When doing the calibration, the beam profiling equipment should bealigned properly, such as a Camera, X-ray or Faraday cups or a Mixtureof these means. The calibration procedure may be rather complicated andtime-consuming.

In an additive manufacturing system using an electron beam gun there maybe at least four signals to calibrate for each beam focus value:Astigmatic coil X, Astigmatic coil Y, Deflection coil X, Deflection coilY.

Here the origin represents the coil signals for the minimum spot size(step 1 above) and the values on the y axis are the obtained optimizedvalues when changing focus (step 2 above).

If the gun is perfectly linear and there are no external fields presentboth astigmatism and deflection compensation will be zero in the centerof the gun (r=0, aligned with the optical axis). As the radii (distanceto the optical axis) increases, the astigmatic values will increasealthough they will be constant in a specific point even if the focuschanges, see FIG. 6. The deflection coils signals obtained in a specificpoint when increasing focus will increase linear with the focus values(F=v×B), see FIG. 5. However if there are effects such as bad alignmentand/or external fields present all the curves may have different levelsand/or different shapes. Thus, it may be important to calibrate thesystem over the entire work area.

In the daily use of an additive manufacturing system it may not bepossible to perform a complete calibration. Instead there is a need fora robust and simple verification procedure.

In a second step 420 the at least two positions 270 of the energy beamspot created with the energy beam 260 having the first focus isdetecting on the work table 250. The detection may be performed by acamera 230, 304.

An image may be taken by the camera 230, 304 provided inside or outsidethe vacuum chamber 320. The camera 230, 304 may be any type of camerafor example an IR-camera (Infrared-camera), NIR-camera (NearInfrared-camera), a VISNIR-camera (Visual Near Infrared-camera), a CCDcamera (Charged Coupled Device-camera), a CMOS-camera (ComplementaryMetal Oxide Semiconductor-camera), a digital camera.

The pattern may be engraved in the work table, i.e., the surface of thework table is melted. Alternatively the energy beam may only reflect theenergy beam in the pattern, i.e., the surface of the work table is notmelted. The image of the full pattern may be compiled from a number ofdifferent images taken at different times during the production of thepattern.

In a third step 430 the energy beam having a second focus is provided inthe at least two positions on a work table. The second focus may be anybe chosen arbitrarily as long as it is different to the first focus.

In a forth step 440 the at least two positions of the energy beam spotcreated with the energy beam having the second focus, is detected on thework table. It may be detected using the same equipment as used fordetecting the position of the at least two positions with the firstfocus. The second focus may be negative or positive.

In a fifth step 450 the at least two positions created with the firstand second focus are compared, wherein the position of the energy beamis verified if the at least two positions created with the first focusare deviating less than a predetermined distance from the at least twopositions created with the second focus.

FIG. 7 depicts an example embodiment of a pattern 710 with a verifiedposition. A regular equidistance dot pattern 710 is first provided on awork table 700 with a first focus. The first focus is symbolized in FIG.7 with circles. The same regular equidistance dot pattern is thenprovided on the work table with a second focus. The second focus issymbolized in FIG. 7 with crosses.

In FIG. 7 the pattern for the two different focuses are superimposed oneach other without any lateral offset of the two patterns. In FIG. 7 theposition can be the to be verified since corresponding positions withthe first and second focuses are not deviating more than a predetermineddistance, here the predetermined distance is zero.

A predetermined allowable distance (offset) may in a first exampleembodiment be less than 100 μm. In an additive manufacturing process theoffset may be accepted to be larger or smaller than the 100 μm dependingon the type of product to be manufactured. Parts with high tolerancerequirements may need an offset in the range of 50 μm in order to beaccepted and parts with low tolerance requirements may accept an offsetlarger than 200 μm.

A translation direction of the first position in relation to the secondposition may give information on how to adjust the deflection deviationwith the deflection coil(s). The translation direction may vary in twodimensions, i.e., translated in both X and Y direction. The idea is toprovide the same pattern with different focuses. A deviation between aposition produced with a first focus compared with a second focus maygive information to the operator that the position calibration isincorrect. The verification of the position may be used as acontrol/quality feature in an additive manufacturing apparatus. If theposition is determined to be out of specification a warning signal maybe sent to the operator of the machine. In an alternative embodimentwhen the position is determined to be out of specification the additivemanufacturing machine may be switched off or put in an idle state.

The work table may be provided with a reference pattern. This referencepattern may be used for calibrating the relative position but also fordetecting other deviations in the energy beam train.

FIG. 1 depicts a schematic side view of an electron beam 140 and itsposition variations when the electron beam focus is varied. An electronbeam is emanating from a filament 110. A deflection coil 130 is capableof deflecting the electron beam 140 at any desired position within agiven maximum area on a work table 150. A focus coil 120 is capable offocusing an electron beam 140 at the work table 150. An astigmatism coil115 is capable of altering a shape of the beam spot. When a focus of anelectron beam is changed, its position will change. In FIG. 1, threedifferent beam focuses are illustrated. A first electron beam is infocus, i.e., with its focus on the work plate 150. A second one has apositive focus, i.e., its focus is above the work table 150. A third onehas a negative focus, i.e., its focus is below the work table 150. Adistance “a” denotes the lateral distance on the work table 150 betweenthe in focus beam and the negative focus beam. A distance “b” denotesthe lateral distance on the work table 150 between the in focus beam andthe positive focus beam.

Deflection coil(s), astigmatism coil(s), focus coils(s) and beam currentmay be controlled by controlled unit 140.

The deflection speed of the electron beam may be altered by changing themagnetic field of the deflection coil, i.e., by ramping the electricalcurrent in the deflection coil at different speeds, where a higherramping speed will result in a larger deflection speed than a lowerramping speed.

In another aspect of the invention it is provided a program elementconfigured and arranged when executed on a computer to implement amethod as described herein. The program element may be installed in acomputer readable storage medium. The computer readable storage mediummay be any one of the control units 140, 240, and/or 350, as describedelsewhere herein. The computer readable storage medium and the programelement, which may comprise computer-readable program code portionsembodied therein, may further be contained within a non-transitorycomputer program product. Further details regarding these features andconfigurations are provided, in turn, below.

As mentioned, various embodiments of the present invention may beimplemented in various ways, including as non-transitory computerprogram products. A computer program product may include anon-transitory computer-readable storage medium storing applications,programs, program modules, scripts, source code, program code, objectcode, byte code, compiled code, interpreted code, machine code,executable instructions, and/or the like (also referred to herein asexecutable instructions, instructions for execution, program code,and/or similar terms used herein interchangeably). Such non-transitorycomputer-readable storage media include all computer-readable media(including volatile and non-volatile media).

In one embodiment, a non-volatile computer-readable storage medium mayinclude a floppy disk, flexible disk, hard disk, solid-state storage(SSS) (e.g., a solid state drive (SSD), solid state card (SSC), solidstate module (SSM)), enterprise flash drive, magnetic tape, or any othernon-transitory magnetic medium, and/or the like. A non-volatilecomputer-readable storage medium may also include a punch card, papertape, optical mark sheet (or any other physical medium with patterns ofholes or other optically recognizable indicia), compact disc read onlymemory (CD-ROM), compact disc compact disc-rewritable (CD-RW), digitalversatile disc (DVD), Blu-ray disc (BD), any other non-transitoryoptical medium, and/or the like. Such a non-volatile computer-readablestorage medium may also include read-only memory (ROM), programmableread-only memory (PROM), erasable programmable read-only memory (EPROM),electrically erasable programmable read-only memory (EEPROM), flashmemory (e.g., Serial, NAND, NOR, and/or the like), multimedia memorycards (MMC), secure digital (SD) memory cards, SmartMedia cards,CompactFlash (CF) cards, Memory Sticks, and/or the like. Further, anon-volatile computer-readable storage medium may also includeconductive-bridging random access memory (CBRAM), phase-change randomaccess memory (PRAM), ferroelectric random-access memory (FeRAM),non-volatile random-access memory (NVRAM), magnetoresistiverandom-access memory (MRAM), resistive random-access memory (RRAM),Silicon-Oxide-Nitride-Oxide-Silicon memory (SONOS), floating junctiongate random access memory (FJG RAM), Millipede memory, racetrack memory,and/or the like.

In one embodiment, a volatile computer-readable storage medium mayinclude random access memory (RAM), dynamic random access memory (DRAM),static random access memory (SRAM), fast page mode dynamic random accessmemory (FPM DRAM), extended data-out dynamic random access memory (EDODRAM), synchronous dynamic random access memory (SDRAM), double datarate synchronous dynamic random access memory (DDR SDRAM), double datarate type two synchronous dynamic random access memory (DDR2 SDRAM),double data rate type three synchronous dynamic random access memory(DDR3 SDRAM), Rambus dynamic random access memory (RDRAM), TwinTransistor RAM (TTRAM), Thyristor RAM (T-RAM), Zero-capacitor (Z-RAM),Rambus in-line memory module (RIMM), dual in-line memory module (DIMM),single in-line memory module (SIMM), video random access memory VRAM,cache memory (including various levels), flash memory, register memory,and/or the like. It will be appreciated that where embodiments aredescribed to use a computer-readable storage medium, other types ofcomputer-readable storage media may be substituted for or used inaddition to the computer-readable storage media described above.

As should be appreciated, various embodiments of the present inventionmay also be implemented as methods, apparatus, systems, computingdevices, computing entities, and/or the like, as have been describedelsewhere herein. As such, embodiments of the present invention may takethe form of an apparatus, system, computing device, computing entity,and/or the like executing instructions stored on a computer-readablestorage medium to perform certain steps or operations. However,embodiments of the present invention may also take the form of anentirely hardware embodiment performing certain steps or operations.

Various embodiments are described below with reference to block diagramsand flowchart illustrations of apparatuses, methods, systems, andcomputer program products. It should be understood that each block ofany of the block diagrams and flowchart illustrations, respectively, maybe implemented in part by computer program instructions, e.g., aslogical steps or operations executing on a processor in a computingsystem. These computer program instructions may be loaded onto acomputer, such as a special purpose computer or other programmable dataprocessing apparatus to produce a specifically-configured machine, suchthat the instructions which execute on the computer or otherprogrammable data processing apparatus implement the functions specifiedin the flowchart block or blocks.

These computer program instructions may also be stored in acomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including computer-readableinstructions for implementing the functionality specified in theflowchart block or blocks. The computer program instructions may also beloaded onto a computer or other programmable data processing apparatusto cause a series of operational steps to be performed on the computeror other programmable apparatus to produce a computer-implementedprocess such that the instructions that execute on the computer or otherprogrammable apparatus provide operations for implementing the functionsspecified in the flowchart block or blocks.

Accordingly, blocks of the block diagrams and flowchart illustrationssupport various combinations for performing the specified functions,combinations of operations for performing the specified functions andprogram instructions for performing the specified functions. It shouldalso be understood that each block of the block diagrams and flowchartillustrations, and combinations of blocks in the block diagrams andflowchart illustrations, could be implemented by special purposehardware-based computer systems that perform the specified functions oroperations, or combinations of special purpose hardware and computerinstructions.

FIG. 8 is a block diagram of an exemplary system 1020 that can be usedin conjunction with various embodiments of the present invention. In atleast the illustrated embodiment, the system 1020 may include one ormore central computing devices 1110, one or more distributed computingdevices 1120, and one or more distributed handheld or mobile devices1300, all configured in communication with a central server 1200 (orcontrol unit) via one or more networks 1130. While FIG. 8 illustratesthe various system entities as separate, standalone entities, thevarious embodiments are not limited to this particular architecture.

According to various embodiments of the present invention, the one ormore networks 1130 may be capable of supporting communication inaccordance with any one or more of a number of second-generation (2G),2.5G, third-generation (3G), and/or fourth-generation (4G) mobilecommunication protocols, or the like. More particularly, the one or morenetworks 1130 may be capable of supporting communication in accordancewith 2G wireless communication protocols IS-136 (TDMA), GSM, and IS-95(CDMA). Also, for example, the one or more networks 1130 may be capableof supporting communication in accordance with 2.5G wirelesscommunication protocols GPRS, Enhanced Data GSM Environment (EDGE), orthe like. In addition, for example, the one or more networks 1130 may becapable of supporting communication in accordance with 3G wirelesscommunication protocols such as Universal Mobile Telephone System (UMTS)network employing Wideband Code Division Multiple Access (WCDMA) radioaccess technology. Some narrow-band AMPS (NAMPS), as well as TACS,network(s) may also benefit from embodiments of the present invention,as should dual or higher mode mobile stations (e.g., digital/analog orTDMA/CDMA/analog phones). As yet another example, each of the componentsof the system 1020 may be configured to communicate with one another inaccordance with techniques such as, for example, radio frequency (RF),Bluetooth™, infrared (IrDA), or any of a number of different wired orwireless networking techniques, including a wired or wireless PersonalArea Network (“PAN”), Local Area Network (“LAN”), Metropolitan AreaNetwork (“MAN”), Wide Area Network (“WAN”), or the like.

Although the device(s) 1110-1300 are illustrated in FIG. 8 ascommunicating with one another over the same network 1130, these devicesmay likewise communicate over multiple, separate networks.

According to one embodiment, in addition to receiving data from theserver 1200, the distributed devices 1110, 1120, and/or 1300 may befurther configured to collect and transmit data on their own. In variousembodiments, the devices 1110, 1120, and/or 1300 may be capable ofreceiving data via one or more input units or devices, such as a keypad,touchpad, barcode scanner, radio frequency identification (RFID) reader,interface card (e.g., modem, etc.) or receiver. The devices 1110, 1120,and/or 1300 may further be capable of storing data to one or morevolatile or non-volatile memory modules, and outputting the data via oneor more output units or devices, for example, by displaying data to theuser operating the device, or by transmitting data, for example over theone or more networks 1130.

In various embodiments, the server 1200 includes various systems forperforming one or more functions in accordance with various embodimentsof the present invention, including those more particularly shown anddescribed herein. It should be understood, however, that the server 1200might include a variety of alternative devices for performing one ormore like functions, without departing from the spirit and scope of thepresent invention. For example, at least a portion of the server 1200,in certain embodiments, may be located on the distributed device(s)1110, 1120, and/or the handheld or mobile device(s) 1300, as may bedesirable for particular applications. As will be described in furtherdetail below, in at least one embodiment, the handheld or mobiledevice(s) 1300 may contain one or more mobile applications 1330 whichmay be configured so as to provide a user interface for communicationwith the server 1200, all as will be likewise described in furtherdetail below.

FIG. 9A is a schematic diagram of the server 1200 according to variousembodiments. The server 1200 includes a processor 1230 that communicateswith other elements within the server via a system interface or bus1235. Also included in the server 1200 is a display/input device 1250for receiving and displaying data. This display/input device 1250 maybe, for example, a keyboard or pointing device that is used incombination with a monitor. The server 1200 further includes memory1220, which typically includes both read only memory (ROM) 1226 andrandom access memory (RAM) 1222. The server's ROM 1226 is used to storea basic input/output system 1224 (BIOS), containing the basic routinesthat help to transfer information between elements within the server1200. Various ROM and RAM configurations have been previously describedherein.

In addition, the server 1200 includes at least one storage device orprogram storage 210, such as a hard disk drive, a floppy disk drive, aCD Rom drive, or optical disk drive, for storing information on variouscomputer-readable media, such as a hard disk, a removable magnetic disk,or a CD-ROM disk. As will be appreciated by one of ordinary skill in theart, each of these storage devices 1210 are connected to the system bus1235 by an appropriate interface. The storage devices 1210 and theirassociated computer-readable media provide nonvolatile storage for apersonal computer. As will be appreciated by one of ordinary skill inthe art, the computer-readable media described above could be replacedby any other type of computer-readable media known in the art. Suchmedia include, for example, magnetic cassettes, flash memory cards,digital video disks, and Bernoulli cartridges.

Although not shown, according to an embodiment, the storage device 1210and/or memory of the server 1200 may further provide the functions of adata storage device, which may store historical and/or current deliverydata and delivery conditions that may be accessed by the server 1200. Inthis regard, the storage device 1210 may comprise one or more databases.The term “database” refers to a structured collection of records or datathat is stored in a computer system, such as via a relational database,hierarchical database, or network database and as such, should not beconstrued in a limiting fashion.

A number of program modules (e.g., exemplary modules 1400-1700)comprising, for example, one or more computer-readable program codeportions executable by the processor 1230, may be stored by the variousstorage devices 1210 and within RAM 1222. Such program modules may alsoinclude an operating system 1280. In these and other embodiments, thevarious modules 1400, 1500, 1600, 1700 control certain aspects of theoperation of the server 1200 with the assistance of the processor 1230and operating system 1280. In still other embodiments, it should beunderstood that one or more additional and/or alternative modules mayalso be provided, without departing from the scope and nature of thepresent invention.

In various embodiments, the program modules 1400, 1500, 1600, 1700 areexecuted by the server 1200 and are configured to generate one or moregraphical user interfaces, reports, instructions, and/ornotifications/alerts, all accessible and/or transmittable to varioususers of the system 1020. In certain embodiments, the user interfaces,reports, instructions, and/or notifications/alerts may be accessible viaone or more networks 1130, which may include the Internet or otherfeasible communications network, as previously discussed.

In various embodiments, it should also be understood that one or more ofthe modules 1400, 1500, 1600, 1700 may be alternatively and/oradditionally (e.g., in duplicate) stored locally on one or more of thedevices 1110, 1120, and/or 1300 and may be executed by one or moreprocessors of the same. According to various embodiments, the modules1400, 1500, 1600, 1700 may send data to, receive data from, and utilizedata contained in one or more databases, which may be comprised of oneor more separate, linked and/or networked databases.

Also located within the server 1200 is a network interface 1260 forinterfacing and communicating with other elements of the one or morenetworks 1130. It will be appreciated by one of ordinary skill in theart that one or more of the server 1200 components may be locatedgeographically remotely from other server components. Furthermore, oneor more of the server 1200 components may be combined, and/or additionalcomponents performing functions described herein may also be included inthe server.

While the foregoing describes a single processor 1230, as one ofordinary skill in the art will recognize, the server 1200 may comprisemultiple processors operating in conjunction with one another to performthe functionality described herein. In addition to the memory 1220, theprocessor 1230 can also be connected to at least one interface or othermeans for displaying, transmitting and/or receiving data, content or thelike. In this regard, the interface(s) can include at least onecommunication interface or other means for transmitting and/or receivingdata, content or the like, as well as at least one user interface thatcan include a display and/or a user input interface, as will bedescribed in further detail below. The user input interface, in turn,can comprise any of a number of devices allowing the entity to receivedata from a user, such as a keypad, a touch display, a joystick or otherinput device.

Still further, while reference is made to the “server” 1200, as one ofordinary skill in the art will recognize, embodiments of the presentinvention are not limited to traditionally defined server architectures.Still further, the system of embodiments of the present invention is notlimited to a single server, or similar network entity or mainframecomputer system. Other similar architectures including one or morenetwork entities operating in conjunction with one another to providethe functionality described herein may likewise be used withoutdeparting from the spirit and scope of embodiments of the presentinvention. For example, a mesh network of two or more personal computers(PCs), similar electronic devices, or handheld portable devices,collaborating with one another to provide the functionality describedherein in association with the server 1200 may likewise be used withoutdeparting from the spirit and scope of embodiments of the presentinvention.

According to various embodiments, many individual steps of a process mayor may not be carried out utilizing the computer systems and/or serversdescribed herein, and the degree of computer implementation may vary, asmay be desirable and/or beneficial for one or more particularapplications.

FIG. 9B provides an illustrative schematic representative of a mobiledevice 1300 that can be used in conjunction with various embodiments ofthe present invention. Mobile devices 1300 can be operated by variousparties. As shown in FIG. 9B, a mobile device 1300 may include anantenna 1312, a transmitter 1304 (e.g., radio), a receiver 1306 (e.g.,radio), and a processing element 1308 that provides signals to andreceives signals from the transmitter 1304 and receiver 1306,respectively.

The signals provided to and received from the transmitter 1304 and thereceiver 1306, respectively, may include signaling data in accordancewith an air interface standard of applicable wireless systems tocommunicate with various entities, such as the server 1200, thedistributed devices 1110, 1120, and/or the like. In this regard, themobile device 1300 may be capable of operating with one or more airinterface standards, communication protocols, modulation types, andaccess types. More particularly, the mobile device 1300 may operate inaccordance with any of a number of wireless communication standards andprotocols. In a particular embodiment, the mobile device 1300 mayoperate in accordance with multiple wireless communication standards andprotocols, such as GPRS, UMTS, CDMA2000, 1×RTT, WCDMA, TD-SCDMA, LTE,E-UTRAN, EVDO, HSPA, HSDPA, Wi-Fi, WiMAX, UWB, IR protocols, Bluetoothprotocols, USB protocols, and/or any other wireless protocol.

Via these communication standards and protocols, the mobile device 1300may according to various embodiments communicate with various otherentities using concepts such as Unstructured Supplementary Service data(USSD), Short Message Service (SMS), Multimedia Messaging Service (MMS),Dual-Tone Multi-Frequency Signaling (DTMF), and/or Subscriber IdentityModule Dialer (SIM dialer). The mobile device 1300 can also downloadchanges, add-ons, and updates, for instance, to its firmware, software(e.g., including executable instructions, applications, programmodules), and operating system.

According to one embodiment, the mobile device 1300 may include alocation determining device and/or functionality. For example, themobile device 1300 may include a GPS module adapted to acquire, forexample, latitude, longitude, altitude, geocode, course, and/or speeddata. In one embodiment, the GPS module acquires data, sometimes knownas ephemeris data, by identifying the number of satellites in view andthe relative positions of those satellites.

The mobile device 1300 may also comprise a user interface (that caninclude a display 1316 coupled to a processing element 1308) and/or auser input interface (coupled to a processing element 308). The userinput interface can comprise any of a number of devices allowing themobile device 1300 to receive data, such as a keypad 1318 (hard orsoft), a touch display, voice or motion interfaces, or other inputdevice. In embodiments including a keypad 1318, the keypad can include(or cause display of) the conventional numeric (0-9) and related keys(#, *), and other keys used for operating the mobile device 1300 and mayinclude a full set of alphabetic keys or set of keys that may beactivated to provide a full set of alphanumeric keys. In addition toproviding input, the user input interface can be used, for example, toactivate or deactivate certain functions, such as screen savers and/orsleep modes.

The mobile device 1300 can also include volatile storage or memory 1322and/or non-volatile storage or memory 1324, which can be embedded and/ormay be removable. For example, the non-volatile memory may be ROM, PROM,EPROM, EEPROM, flash memory, MMCs, SD memory cards, Memory Sticks,CBRAM, PRAM, FeRAM, RRAM, SONOS, racetrack memory, and/or the like. Thevolatile memory may be RAM, DRAM, SRAM, FPM DRAM, EDO DRAM, SDRAM, DDRSDRAM, DDR2 SDRAM, DDR3 SDRAM, RDRAM, RIMM, DIMM, SIMM, VRAM, cachememory, register memory, and/or the like. The volatile and non-volatilestorage or memory can store databases, database instances, databasemapping systems, data, applications, programs, program modules, scripts,source code, object code, byte code, compiled code, interpreted code,machine code, executable instructions, and/or the like to implement thefunctions of the mobile device 1300.

The mobile device 1300 may also include one or more of a camera 1326 anda mobile application 1330. The camera 1326 may be configured accordingto various embodiments as an additional and/or alternative datacollection feature, whereby one or more items may be read, stored,and/or transmitted by the mobile device 1300 via the camera. The mobileapplication 1330 may further provide a feature via which various tasksmay be performed with the mobile device 1300. Various configurations maybe provided, as may be desirable for one or more users of the mobiledevice 1300 and the system 1020 as a whole.

The invention is not limited to the above-described embodiments and manymodifications are possible within the scope of the following claims.Such modifications may, for example, involve using a different source ofenergy beam than the exemplified electron beam such as a laser beam.Other materials than metallic powder may be used, such as thenon-limiting examples of: electrically conductive polymers and powder ofelectrically conductive ceramics. Images taken from more than 2 layersmay also be possible, i.e., in an alternative embodiment of the presentinvention for detecting a defect at least one image from at least three,four or more layers are used. A defect may be detected if the defectposition in the three, four or more layers are at least partlyoverlapping each other. The thinner the powder layer the more powderlayers may be used in order to detect a factual defect.

Indeed, a person of ordinary skill in the art would be able to use theinformation contained in the preceding text to modify variousembodiments of the invention in ways that are not literally described,but are nevertheless encompassed by the attached claims, for theyaccomplish substantially the same functions to reach substantially thesame results. Therefore, it is to be understood that the invention isnot limited to the specific embodiments disclosed and that modificationsand other embodiments are intended to be included within the scope ofthe appended claims. Although specific terms are employed herein, theyare used in a generic and descriptive sense only and not for purposes oflimitation.

That which is claimed:
 1. A non-transitory computer program productcomprising at least one non-transitory computer-readable storage mediumhaving computer-readable program code portions embodied therein, thecomputer-readable program code portions comprising: at least oneexecutable portion configured for: providing said energy beam having afirst focus in at least two positions on said work table, detecting saidat least two positions of said energy beam spot on said work tablecreated with said energy beam having said first focus, providing saidenergy beam having a second focus in said at least two positions on saidwork table, and detecting said at least two positions of said energybeam spot on said work table created with said energy beam having saidsecond focus, and at least one executable portion configured forcomparing said at least two positions created with said first and secondfocuses, wherein said position of the energy beam is verified if said atleast two positions created with said first focus are deviating lessthan a predetermined distance from said at least two positions createdwith said second focus.
 2. The non-transitory computer program productof claim 1, wherein: said computer program product is configured forverifying a deflection speed; and said computer program product furthercomprises: an executable portion configured for generating apredetermined pattern on a work table with said energy beam spot whiledeflecting said energy beam spot with a first deflection speed; anexecutable portion configured for detecting first positions of saidenergy beam spot on said work table created with said first deflectionspeed; an executable portion configured for generating saidpredetermined pattern on a work table with said energy beam spot whiledeflecting said energy beam spot with a second deflection speed; anexecutable portion configured for detecting second positions of saidenergy beam spot on said work table created with said second deflectionspeed; and an executable portion configured for comparing said first andsecond positions, wherein said deflection speed is verified if each oneof said first positions are deviating less than a predetermined distancefrom corresponding ones of said second positions.
 3. The non-transitorycomputer program product of claim 2, wherein: said computer programproduct is configured for verifying a beam spot size; and said computerprogram product further comprises: an executable portion configured forgenerating a first energy beam spot from a first energy beam sourcehaving a predetermined size and power at a first position on a workpiece, an executable portion configured for varying at least one of afocus lens setting or an astigmatism lens setting for said first energybeam spot until max intensity for the first beam spot is detected, anexecutable portion configured for comparing at least one setting of saidfocus lens and/or astigmatism lens for said detected maximum intensityof the first energy beam spot with corresponding stored settings of saidfocus lens and/or astigmatism lens for the first energy beam spot withsaid predetermined size and power, an executable portion configured forrepeating said generating, varying, and comparing steps for differentpredetermined beam powers, and an executable portion configured forrepeating said generating, varying, comparing, and said repetitionthereof steps for different positions on said work piece, wherein saidfirst energy beam spot size is verified if each detected settings ofsaid focus lens and/or astigmatism lens are deviating less than apredetermined value from corresponding stored settings of said focuslens and/or astigmatism lens.
 4. The non-transitory computer programproduct of claim 1, wherein: said computer program product is configuredfor verifying a beam spot size; and said computer program productfurther comprises: an executable portion configured for generating afirst energy beam spot from a first energy beam source having apredetermined size and power at a first position on a work piece, anexecutable portion configured for varying at least one of a focus lenssetting or an astigmatism lens setting for said first energy beam spotuntil max intensity for the first beam spot is detected, an executableportion configured for comparing at least one setting of said focus lensand/or astigmatism lens for said detected maximum intensity of the firstenergy beam spot with corresponding stored settings of said focus lensand/or astigmatism lens for the first energy beam spot with saidpredetermined size and power, an executable portion configured forrepeating said generating, varying, and comparing steps for differentpredetermined beam powers, and an executable portion configured forrepeating said generating, varying, comparing, and said repetitionthereof steps for different positions on said work piece, wherein saidfirst energy beam spot size is verified if each detected settings ofsaid focus lens and/or astigmatism lens are deviating less than apredetermined value from corresponding stored settings of said focuslens and/or astigmatism lens.
 5. An apparatus for verifying a positionof an energy beam spot, said apparatus comprising: at least one energybeam source configured to generate at least one energy beam; and acontrol unit configured to: provide said at least one energy beam havinga first focus in at least two positions on a work table, detect said atleast two positions of said energy beam spot on said work table createdwith said at least one energy beam having said first focus, provide saidat least one energy beam having a second focus in said at least twopositions on a work table, detect said at least two positions of saidenergy beam spot on said work table created with said at least oneenergy beam having said second focus, and compare said at least twopositions created with said first and second focuses, wherein saidposition of the energy beam is verified if said at least two positionscreated with said first focus are deviating less than a predetermineddistance from said at least two positions created with said secondfocus.
 6. The apparatus of claim 5, wherein: the apparatus is furtherconfigured for verifying a deflection speed of said first energy beamspot; and the control unit is further configured to: generate apredetermined pattern on a work table with said energy beam spot whiledeflecting said energy beam spot with a first deflection speed; detectfirst deflection positions of said energy beam spot on said work tablecreated with said first deflection speed; generate said predeterminedpattern on a work table with said energy beam spot while deflecting saidenergy beam spot with a second deflection speed; detect seconddeflection positions of said energy beam spot on said work table createdwith said second deflection speed; and compare said first and seconddeflection positions, wherein said deflection speed is verified if eachone of said first deflection positions are deviating less than apredetermined distance from corresponding ones of said second deflectionpositions.
 7. The apparatus of claim 6, wherein: the apparatus isfurther configured for verifying a size of at least one energy beamspot; and the control unit is further configured to: vary at least oneof a focus lens setting or an astigmatism lens setting for said firstenergy beam spot until max intensity for the first beam spot isdetected, compare at least one setting of said focus lens and/orastigmatism lens for said detected maximum intensity of the first energybeam spot with corresponding stored settings of said focus lens and/orastigmatism lens for the first energy beam spot with said predeterminedsize and power, repeat said generating, varying, and comparing steps forone or more beam powers other than said predetermined beam power, andrepeat said generating, varying, comparing, and the above repeatingsteps for one or more positions on said work piece other than said firstposition, wherein said first energy beam spot size is verified if eachdetected settings of said focus lens and/or astigmatism lens aredeviating less than a predetermined value from corresponding storedsettings of said focus lens and/or astigmatism lens.
 8. The apparatus ofclaim 5, wherein: the apparatus is further configured for verifying asize of at least one energy beam spot; and the control unit is furtherconfigured to: vary at least one of a focus lens setting or anastigmatism lens setting for said first energy beam spot until maxintensity for the first beam spot is detected, compare at least onesetting of said focus lens and/or astigmatism lens for said detectedmaximum intensity of the first energy beam spot with correspondingstored settings of said focus lens and/or astigmatism lens for the firstenergy beam spot with said predetermined size and power, repeat saidgenerating, varying, and comparing steps for one or more beam powersother than said predetermined beam power, and repeat said generating,varying, comparing, and the above repeating steps for one or morepositions on said work piece other than said first position, whereinsaid first energy beam spot size is verified if each detected settingsof said focus lens and/or astigmatism lens are deviating less than apredetermined value from corresponding stored settings of said focuslens and/or astigmatism lens.
 9. A method for forming athree-dimensional article through successively depositing individuallayers of powder material that are fused together with at least oneenergy beam so as to form the article, said method comprising the stepsof: generating a model of said three dimensional article, applying afirst powder layer on a work table, directing said energy beam from atleast one energy beam source over said work table, causing said firstpowder layer to fuse in selected locations according to said model toform a first cross section of said three dimensional article, saidmethod further comprising a verification method for verifying a positionof said energy beam used for fusing said powder material, saidverification method comprising the steps of: providing said energy beamhaving a first focus in at least two positions on said work table,detecting said at least two positions of said energy beam spot on saidwork table created with said energy beam having said first focus,providing said energy beam having a second focus in said at least twopositions on said work table, detecting said at least two positions ofsaid energy beam spot on said work table created with said energy beamhaving said second focus, and comparing said at least two positionscreated with said first and second focuses, wherein said position of theenergy beam is verified if said at least two positions created with saidfirst focus are deviating less than a predetermined distance from saidat least two positions created with said second focus.
 10. The methodaccording to claim 9, wherein said verification method is performedbefore each layer of said three-dimensional article is fused.
 11. Themethod according to claim 10, wherein said verification method isperformed while applying powder on said work table.
 12. The methodaccording to claim 9, wherein said verification method is performed onat least one of fused areas or non-fused areas.